Office space dividing systems, such as the office space dividing system described in U.S. Pat. No. 3,762,116, often require one or more panels which include a translucent or transparent sheet of material. While such sheet material may be in the form of plastic or glass, it will be hereinafter referred to simply as "glass", in order to facilitate the description of the invention. Such a panel includes a metallic frame constructed of rails and stiles to form a window, with inner facing edges of the frame having channels which collectively define a continuous annular channel for receiving the perimetrical edges of the glass. Because of the weight of such panels, and the possibility of scratching, breaking, or otherwise damaging the glass, it is common to ship the frame and glass separately, for assembly at the job site. It is also common to sell panels or frames with no glass, so the user can add glass when desired, or add "customized" glass. The frames, however, collect dirt and debris in the channels, requiring a time consuming cleaning operation to prepare the channels for receiving the glass.